A new antibacterial ointment could help take down drug-resistant bacteria.

In human skin samples and mice, the medicine completely cleared wounds of MRSA, the strain of Staphylococcus aureus that is resistant to methicillin and other antibiotics, and antibiotic-resistant Acinetobacter baumannii. Both microbes are known to cause serious infections in hospital patients. Researchers in the Netherlands created the gel’s key ingredient, a chain of amino acids called SAAP-148, by improving on a bacteria-fighting peptide found in humans.

The synthetic peptide prevents pathogens from forming biofilms — colonies of microbes enveloped in a protective slime that shields them from antibiotics, the researchers report online January 10 in Science Translational Medicine. Bacteria living in a biofilm can be 10 to 1,000 times as hard to kill as their free-floating counterparts. SAAP-148 also wiped out microbes that hunker down in a dormant, drug-tolerant state during an antibiotic assault, then lead the bacterial resurgence after treatment ends.

“This peptide could provide a much-needed boost to our arsenal of antibiotics,” says David Weiss, a microbiologist at Emory University School of Medicine in Atlanta, who wasn’t involved in the work.

Unlike S. aureus and A. baumannii bacteria exposed to conventional antibiotics in the study, the microbes didn’t develop strong resistance to SAAP-148 after at least a couple weeks’ exposure to the compound. These results are “quite promising,” says Weiss, who would like to see the peptide tested against other bacteria as well. Studies of the gel in humans will begin this year.